The successful use of extruded tubes of expanded polytetrafluoroethylene (ePTFE) as a synthetic implantable vascular prostheses or tubular graft, designed in particular for the application of synthetic vascular prosthesis or tubular grafts is well known and documented. ePTFE, validated through significant clinical studies, is particularly suitable as a vascular prosthesis or tubular graft as it exhibits superior bio-compatibility and can be mechanically manipulated to form a well defined porous microstructure known to promote endothelialization. PTFE has proven to exhibit a low thrombogenic response in vascular applications. When seeded or infused with a cardio protective agent, the microporous structure, formed anodes and fibrils, allows natural tissue ingrowth and cell endothelialization when implanted in the vascular system. This contributes to long term healing and patency of the tubular graft.
In the prior art, U.S. Pat. No. 6,436,135 Goldfarb, the microstructure of a synthetic vascular prostheses or tubular graft formed of ePTFE is categorized by a fibrous state which is further defined by irregularly spaced nodes interconnected by elongated fibrils or microfibers. The method and techniques for creating this structure have been known for more than three decades and is, in fact, quite simple to one skilled in the art. The distance between the node surfaces that is spanned by the fibrils is defined as the inter-nodal distance (IND). A tubular graft having a specific range of IND enhances tissue ingrowth and cell endothelialization as the tubular graft is inherently porous. The IND range is also small enough to prevent transmural blood flow and thrombosis but not less than the maximum dimension of the average red blood cell, between 6μ and 80μ.
The prior art is filled with examples of microporous ePTFE tubular vascular prosthesis or tubular grafts. The porosity of an ePTFE vascular prosthesis or tubular graft is controlled by the mechanical formation of the IND or the microporous structure of the tube. IND with the defined structure referenced produces results of tissue ingrowth as well as cell endothelialization along the inner and outer surface of the vascular prosthesis or tubular graft.
Similarly, stents are commonly used to restore and maintain body passages, such as blood vessels. Often, biocompatible materials, including grafts, can be provided on the inner or outer surfaces of the stent to reduce reactions associated with contact of the stent with the body.
However, it is difficult with such conventional devices to manipulate mechanical properties, cellular proliferation, cellular permeability, fluid permeability, adhesion to a structural frame, and/or incorporation of an active therapeutic component in the same. Further, such conventional devices do not allow for coating of complex geometries that otherwise could not be covered with ePTFE or other materials alone.
Thus, a need exists for processes that address the deficiencies described above. Prosthetic devices made from such processes would also be particularly beneficial.